江西相山铀矿田两类流纹英安岩的岩浆演化特征——来自长石和黑云母化学成分证据

欧阳军勇; 张树明; 张鑫; 刘龙; 夏寅初; 吴志春; 万康

doi:10.12029/gc20201110002

江西相山铀矿田两类流纹英安岩的岩浆演化特征——来自长石和黑云母化学成分证据

Magmatic evolution characteristics of two types of rhyolite dacite in Xiangshan uranium ore field——Evidence from chemical composition of feldspar and biotite

摘要

摘要:
研究目的 长石、黑云母等岩浆分异作用形成的矿物可以作为寄主岩石岩浆演化的指示剂。相山流纹英安岩与流纹英安斑岩两者在形成时代、成因归属、物质来源和地幔物质参与等方面存在争议。
研究方法 本文借助电子探针技术对相山两类流纹英安岩中的长石、黑云母进行定量分析，对两者间的成分、物质来源、形成温度、氧逸度和岩石性质等特征进行分析研究，在此基础上探讨两类流纹英安岩的岩浆演化特征。
研究结果 研究结果表明：相山打鼓顶组流纹英安岩可区分为两类，一类是喷溢相的流纹英安岩（K₁d^2a），另一类是侵入相的流纹英安斑岩（K₁d^2b）。流纹英安岩的长石类型较流纹英安斑岩多，其中流纹英安岩的长石类型包括钠长石、钾长石、钾-透长石、更长石、中长石；流纹英安斑岩长石类型主要有钠长石、钾长石和钾-透长石。流纹英安岩与流纹英安斑岩的黑云母形成温度基本相同（750±20℃），均具有高氧逸度，同属钙碱性岩；岩浆物质来源相同，均有幔源物质加入。
结论流纹英安岩与流纹英安斑岩的化学成分基本相同、长石类型相似、物质来源相同、结晶温度相同、氧逸度一致、岩石性质相同，说明两者具有同源性。

Abstract:
This paper is the result of mineral exploration engineering.
Objective Minerals formed by magmatic differentiation, such as feldspar and biotite, can be used as indicators of magmatic evolution of host rocks.There are disputes between rhyodacite and rhyodacite porphyry from Xiangshan, in the aspects of formation age, origin, material source and mantle material participation.
Methods In this paper, the electron probe technology is used to quantitatively analyze the feldspar and biotite in two types of rhyodacites in Xiangshan, and the composition, material source, formation temperature, oxygen fugacity and rock properties of the two types of rhyodacites are analyzed and studied.
Results The results show that the rhyodacite of Xiangshan Daguding Formation can be divided into two types, one is the effusive rhyodacite (K₁d^2a) and the other is the intrusive rhyodacite porphyry (K₁d^2b). The types of feldspar from rhyodacite are more than those of rhyodacite porphyry. The feldspar types of rhyodacite include albite, potassium feldspar, potassium sanidine, feldspar and andesine. The main feldspar types of rhyodacite porphyry are albite, potassium feldspar and potassium-sanidine. The biotite formation temperature of rhyodacite and rhyodacite porphyry is basically the same (750±20℃). Rhyodacite and rhyodacite porphyry both have high oxygen fugacity and belong to calc-alkaline rocks, indicating the same magma material source with part from mantle material.
Conclusions The chemical composition is basically the same, together with the same feldspar type, the same material source, the same crystallization temperature, the sameoxygen fugacity, and the same rock properties, indicating that the two have homology.

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